CareerCup-3.2
How would you design a stack which, in addition to push and pop, also has a function min which returns the minimum element? Push, pop and min should all operate in O(1) time.
微软实习生一面就遇到了这个问题,当时想到的是笨办法。但是面试官一点点引导,终于想出来这么做。
#include <iostream>
using namespace std;
typedef int Data;
// Creating a Linked List:
struct Node
{
Node(Data d=0):data(d){next = NULL;};
Data data;
Node* next;
};
class Stack
{
public:
Stack():top(NULL){minNode = NULL;};
void pop()
{
if(top != NULL)
{
Node* p = top;
top = top->next;
delete p;
Node* m = minNode;
minNode = minNode->next;
delete m;
}
};
Data peek()
{
if(top != NULL)
{
return top->data;
} else {
throw "Empty Stack";
}
};
void push(Data data)
{
Node* d = new Node(data);
d->next = top;
top = d;
if(minNode != NULL && minNode->data < data)
data = minNode->data;
Node *m = new Node(data);
m->next = minNode;
minNode = m;
};
Data min()
{
if(minNode == NULL)
throw "Empty Stack";
else
return minNode->data;
};
bool isEmpty(){return top == NULL;};
private:
Node* top;
Node* minNode;
};
int main()
{
Stack stack;
stack.push(3);
cout<<stack.min()<<endl;
stack.push(2);
cout<<stack.min()<<endl;
stack.pop();
cout<<stack.min()<<endl;
system("pause");
};